Balancing the airflow through a duct system is a necessary step in the effective exploitation of a ventilation system for the heating or cooling of an enclosure such as a home or other type of building.
It is known to exploit an adjustable damper device which has some method of ensuring that the damper does not move once it is adjusted; see, for example, U.S. Pat. No. 4,628,954, U.S. Pat. No. 5,806,830 and U.S. Pat. No. 6,082,704.
U.S. Pat. No. 5,806,830, for example describes an adjustable damper which exploits a conventional wing nut and lever arrangement, positioned on the exterior surface of the duct. The lever is attached directly to a damper valve inside the collar in the air flow. Adjustment is made by loosening the wing nut by hand, maneuvering the lever arrangement into the desired position, and finally tightening the wing nut by hand. The mechanism is, however, not self-locking and therefore is not easily positioned correctly; additionally it may be accidentally dislodged from the desired position over time.
U.S. Pat. No. 6,082,704 describes a damper mechanism whereby the damper valve in a damper collar body is held in position by spring tension which forces gear teeth on the damper rod in the damper collar body into mating engagement with gear teeth also in the inner collar body thus making the damper self-locking. The damper mechanism, however, requires the use of a separate tool to effect adjustments whereby the tool overcomes the biasing of the spring to effect separation of gear teeth and rotation of the damper.
It would be advantageous to have a damper assembly which could be incrementally adjustable as well as self-locking and which may also as desired also avoid the use of a separate tool in order to effect adjustments. It would also be advantageous if the assembly could provide an indication (e.g. on the outside of the assembly) of the position (e.g. maximum open position) of the damper member within the assembly. It would be advantageous if a damper member could rotate freely between a closed position and a pre-determined (i.e. adjustable) maximum damper open position; in other words to have a damper which may permit air flow in one direction while inhibiting air flow in an opposite direction and not exceed a maximum damper open position.